The high resolution IR spectrum of ⁷⁰GeHD₃: analysis of the ν₅ and ν₂/ν₄ bands, and determination of the J- and K-dependent ground state constants

Abstract

High resolution FTIR spectra of monoisotopic ⁷⁰GeHD₃ have been recorded in the region of the ν₁, ν₂/ν₄ and ν₅ bands with a resolution between 0.0021 and 0.004 cm⁻¹. The J-dependent ground state constants up to sextic terms have been determined from ground state combination differences formed from transitions observed in the σ₁ band. The K-dependent parameters C₀ and D^O_K were obtained from 89 perturbation-allowed transitions observed in the ν₂/ν₄ band. These are related to three different K/(K + 3) ground state levels. The ν₅ band, ν₀ = 792.517 cm⁻¹, is separated from other vibrational levels. Fits of rovibrational transitions, J′_max = 29, converged with σ = 1.24 × 10⁻³ cm⁻¹, while σ = 0.30 × 10⁻³ cm⁻¹ was achieved when J′ was truncated to ⩽ 18. The analysis of the ν₂/ν₄ band, ν^O₂ = 1513.527 and ν^O₄ = 1524.122 cm⁻¹, revealed that high-K^R(P, Q, R)_K transitions are affected by as yet unknown perturbers. These were eliminated from the data fit, which gave σ = 1.28 × 10⁻³ cm⁻¹. The presence of an α resonance between ν₂ and ν₄, α^BB_2,4 = 7.551(7) × 10⁻³ cm⁻¹, was established while no effects of the expected Coriolis x, y resonance were evident.